Figure 2.

The transport parameters that produce an exact match with the PDE depend on kinetic parameters (non-thin compartment regime). (a) In the mass action regime, transport parameters can be computed, which can guarantee an exact match, provided that sequestration in the intermediate space is exactly accounted for. However, this exact match is not robust to changes in kinetics, even if sequestration is correctly accounted for. On the other hand, if we account for the kinetic dependence of the transport parameters, the compartmental model continues to produce an exact fit. (b) The percentage error in X ₁ (average concentration of X in compartment 1) is zero at the basal value of kinetic parameter k ₁, and increases when k ₁ is perturbed. (c) Away from the thin compartment regime, D/LL ₁ is a poor choice of transport parameter (triangles). In the non- mass action regime, an exact fit is impossible, but transport parameters may be computed by minimizing the error (sum-squared error). Transport parameters obtained by minimizing the error produce a good match (green circles - maximum error 0.6 percent). However, for these transport parameters, the ability to match the PDE is lost if the kinetics is perturbed.